This invention relates to pressure transmitting devices. More particularly, it relates to means for transmitting the pressure in a hydraulic fluid to inject slurry fuel into combustion chambers such as, for example, those in internal combustion engines.
It is often desirable to use a pressure transmitting device to produce pressure in, and thereby displace a finite volume of, a slurry material, that is, a material having solid particles suspended in a liquid medium. It is also often desirable to use a mechanism which is responsive to a pressurized hydraulic fluid in order to provide this pressurization and displacement of the slurry material. Furthermore, to prevent contamination of the hydraulic fluid by solid particles from the slurry material, it is desirable to substantially isolate the hydraulic fluid from the slurry material. One application where these characteristics are particularly desirable is in a system for injecting slurry fuels into a combustion chamber.
A number of combustion systems are currently candidates for burning solid fuel particles suspended in a liquid medium. In particular, a slurry of coal and water appears to offer significant potential as a substitute for liquid fossil fuels such as, for example, diesel oil. Many of these candidate combustion systems require that the slurry fuel be metered and injected in a highly controlled manner. The fuel injection system must be capable of rapid and accurate operation, over a range of combustor operating conditions. For example, in a diesel engine, the fuel injection system must exhibit the rapid injector opening and closing times typical of conventional diesel fuel injectors, in order to produce the correct burning characteristics in the engine. Diesel engines also require the fuel injection system to operate at relatively high injection pressures, with the pressure exceeding 3000 pounds per square inch in some applications.
Conventional diesel fuel injection systems typically employ a jerk pump to meter and pressurize the diesel oil, and a high pressure needle valve injector to atomize the diesel oil as it enters the combustion chamber. Such a system provides a number of beneficial characteristics, including rapid operation and accurate control of the amount of fuel injected. However, when this type of system is employed to inject a slurry fuel, the solid particles in the slurry tend to become wedged in the clearance gaps between the adjacent surfaces of the sliding parts of the jerk pump and the injector. What is needed, then, is a way to maintain these clearance gaps free from solid fuel particles.
It is an object of the present invention to provide an apparatus for transmitting pressure from a hydraulic fluid to a material having solid particles suspended in a liquid medium.
It is also an object of the present invention to substantially isolate the hydraulic fluid from the solid particles of the material.
It is a further object of the present invention to provide a pressure transmitting apparatus which may be readily employed in a slurry fuel injection system.